My research focuses on the ecology of freshwater fishes. Research in my lab is conducted on a variety of organizational levels from the physiology of individuals to community dynamics over large spatial and temporal scales. Some recently completed projects included studies on developmental plasticity of physiological traits3, ecomorphology of sculpin2, evolution of reproductive isolation in topminnows, and techniques for assessing the magnitude of temporal change in communities5,6.
If you are a student interested in research opportunities in my lab, please contact me.
Electronic copies of recent publicatioins.
One of the greatest challenges in biology is to explain the levels and patterns
of species diversity. Addressing this problem requires a multidisciplinary,
integrative approach with a model system involving a range of temporal (from
historical biogeography to individual life spans) and spatial (from range
wide phenomena to individual interactions) scales. Hybrid zones, where closely
related species interact and potentially hybridize, provide an ideal system
in which to study the evolutionary processes that generate and maintain species
diversity.
Fishes in the Fundulus notatus species complex are found throughout the Midwestern
and Southern United States. The two most widely distributed members of this
complex, F. notatus and F. olivaceus, occur throughout much of the Mississippi
River drainage as well as the coastal drainages of the Gulf of Mexico. Throughout
this range, these two species encounter one another in numerous contact zones.
In contrast, other members of the complex of equal, or older evolutionary
age, like F. euryzonus, are more narrowly distributed and endemic to single
drainages. While members of the complex have similar morphologies and ecologies,
their ranges differ markedly in size, making them an ideal group for these
types of questions. Much of my research interest is currently focused on ecological
and evolutionary questions regarding this system: 1) What is the nature of
the numerous independent contact zones present throughout their ranges? 2)
What are the relative strengths of the various prezygotic (reinforcement)
and postzygotic (endogeonous and exogenous selection) barriers among these
species? and 3) What factors explain the differences in distributional patterns
between broadly distributed and narrowly endemic members of the complex?
Graduate and undergraduate students in my lab are pursuing a variety of
reserach questions on different ecological and evolutionary scales ranging
from biogeography of darters to telemetry of adult and juvenile alligator
gar. Listed below are my current students with summaries of their research
focus.
1) Is there evidence of dietary shift where species-pairs occur syntopically?
2) Do species feed selectively? 3) Does trophic partitioning occur during
periods of decreased prey availability? 4) Do patterns of co-occurrence suggest
partitioning of habitat resources in syntopy? If interspecific competition
occurs in streams, then changes in diets and abundances will be observed in
syntopy. Conversely, allotopic populations can serve as controls based on
the assumption that those individuals will demonstrate food and habitat selectivity
in the absence of competitors. My experimental approach involves monthly sampling
aimed at collecting study pairs of similar species in syntopy and allotropy.
In the second phase of the experiment, experimental streams will be used to
perform a response surface design competition experiment aimed at quantifying
intra- and interspecific competition among sand darters (Ammocrypta beanii
and A. vivax).
Pleistocene glaciations are often cited as the major force shaping the modern distributions of North American freshwater fishes. These hypotheses seem to be strongly corroborated for fishes occurring above the Allegheny-Ouachita-Marathon continental suture; however, glacial effects do not easily explain the distribution of fishes found below the suture on the coastal plain. Glaciation, however, has a corollary in eustasy, or the global rise and fall of sea level. Eustatic effects are known to alter fluvial regimes during highstand or lowstand conditions, but how eustasy has affected the biogeography of freshwater fishes is largely unexplored. I am using the Nothonotus subgenus of darters to study biogeographic patterns in Gulf Coast drainages. Specifically, I ask if morphometrics and nuptial color patternation produce a phylogeny that will resolve the placement of the members of subgenus relative to one other? 2) Is there a preference for large substrates in their habitats? 3) How did the species assigned to this subgenus reach their present day distributions?
Alabama shad (Alosa alabamae) is an anadromous fish listed by NMFS as a candidate species in 1997 (also a USFWS candidate species). Its closest relative is the American shad (A. sapidissima) of Atlantic drainages. Once abundant in the Gulf of Mexico and the Mississippi River drainages, numerous populations have been extirpated with the remaining populations small and isolated. Based on the distribution of extant populations, factors affecting freshwater life stages are likely the primary causes of declines in A. alabamae. The presumed culprits are primarily dams and locks, but also siltation, water pollution, and dredging of sandbars used for. The far-reaching research objectives have been to: 1) determine migration and spawn timing, age of spawning fish, spawning locations, and juvenile migration patterns and growth rates within the drainage, 2) evaluate habitat selection by juveniles and adults , 3) compare habitat use in the Pascagoula River drainage to that used in other drainages, 4) recommend fish and habitat sampling protocols for use with this species in other drainages throughout its range, 5) develop an index of A. alabamae abundance in the Pascagoula River drainage, and 6) use population modeling to identify sensitive life stages to target for future research and conservation actions.
The alligator gar (Atractosteus spatula) historically ranged throughout much
of the lower Mississippi drainage and the gulf coast of Mexico to Veracruz.
Within the Mississippi River drainage, populations existed as far north as
the lower reaches of the Missouri and Ohio Rivers, as far west as the Red
River drainage and Lake Texoma and as far east as the Ecofina River in the
panhandle of Florida. Alligator gar have historically supported a fishery
in the White River system of Arkansas, is a highly valued food fish in northeastern
Mexico and a sport fish in parts of the southeastern United States. Due to
habitat alteration in the north and fishing pressure in the south, populations
of alligator gar are declining throughout much of the range. Once considered
abundant, many northern and western populations in the Mississippi River drainage
are thought to have been extirpated. Restoration efforts are underway in some
of these areas but basic knowledge to alligator gar ecology, population structure
and life history are impeding conservation efforts. The purpose of my research
is to assess movement, dispersal and habitat use in adult and hatchery reared
juvenile alligator gar. I am working with researchers at the Private John
Allen Fish Hatchery (Tupelo, MS) and the Tennessee Department of Natural Resources
on adult and juvenile telemetry studies to address these questions.
I am also curator of the USM Museum of Ichthyology. The
collection is an invaluable resource for students and researchers interested
in ichthyology. The museum currently containes over 30,000 lots and 500,000
specimens representing approximately 700 taxa. While most of the collection
contains fishes from the southeastern US, efforts are underway to add a number
of unique collections from Honduras.
Lutterschmidt, W.I, Schaefer J.F., and Furrillio, R. 2007. Relationships between parasite load and physiological performance (CTMax and endurance) of two Centrarchids (Lepomis megalotis and Lepomis macrochirus). In press, Journal of Comparative Parasitology.
Schaefer, J.F. 2006. A simple and economical method for precise, programmable thermal regimes in recirculating aquatic mesocosms. North American Journal of Aquaculture. 68:240-244.